The purpose of the proposed study is to provide basic parametric information about sensitivity to the orientation of lines and grids in the human at suprathreshold levels of contrast. Specific factors to be explored are the relation between spatial frequency and orientation; memory of orientation; the effects of contrast and of retinal eccentricity; orientation sensitivity in chromatic channels; the effects of grid size and line length; the effects of sustained and transient modes of presenting stimuli; and the relation between orientation and sensitivity to velocity. Procedures for collecting the data and methods for analyzing the results will be guided by two goals: first, to provide information suitable for further development of our understanding of the relation between perceived orientation and the activity of neurons that are sensitive to the orientation, color, spatial frequency, velocity and temporal properties of visual stimuli; and second to explore ways of establishing norms for sensitivity to orientation with a view toward clinical applications of the findings in perceptual disorders such as dyslexia, in brain damage and in various forms of ocular pathology.